A rider is necessarily required to wear a helmet when riding a two-wheeled vehicle such as a motorcycle, and a retractable shield may be installed at a front opening of a helmet main body to allow a helmet wearer to obtain a front view.
Generally, a shield exposed to the outside of a helmet is made of plastic to allow a helmet wearer to obtain a front view and to readily open and close the shield. If a surface of the shield is damaged or scratched by foreign substances or the like, the shield is replaced or a shield protective film is attached on the shield in order to obtain a clear view according to conventional techniques.
A helmet has a hermetically sealed structure where little air can get in or get out, which makes a helmet wearer easily feel it is stuffy inside the helmet. Further, the inside of a shield can be steamed due to humidity caused by the helmet wearer's breathing, and, thus, the helmet wearer's view may be blocked. In order to solve these problems, there has been suggested a helmet including a retractable ventilation unit on each of a front side and a rear side of a helmet main body. With this configuration, air outside the helmet can flow into the helmet and circulate in the helmet and then flow out through the rear side of the helmet main body.
However, generally, a helmet main body is fastened to a helmet wearer's head for safety, and thus, air flowed into through a front side of the helmet cannot flow out smoothly.